Circuit interrupter



Aug. 11, 1953 w. M. LEEDS CIRCUIT INTERRUPTER 4 Sheets-Sheet 1 Filed May 18, 1950 23 l i 6: 2 I} 6 c a nuuu 7 l Q5 5 P: l n B .m 8 m l l m 0 l 9 2 2 2 1i 5 3 LI 5 :3 M.

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INVENTOR Winthrop M. Leeds. BY R/ ATTORNEY WITNESSES: 1 77 2 4% g- 1953 w. M. LEEDS 2,648,745

CIRCUIT INTERRUPTER Filed May 18, 1950 4 Sheets-Sheet 2 Fig.2. T 7 F I94.

4| 59 as o 47 u 43 H 2 24 [8 2| 5| I6 39 64 54 3 IX. 1X 30 Q 22 54 r i'llI 3| 5 WITNESSES: INVENTOR W Winthrop-M. Leeds 4. d; BY-

Aug. 11, 1953 w. M. LEEDS 2,648,745

CIRCUIT INTERRUPTER Filed May 18, 1950 4 Sheets-Sheet 3 WITNESSES: INVENTOR Y Winthrop M. Leeds. a 6%? BY Z ATTORNE Aug. 11, 1953 w. M. LEEDS CIRCUIT INTERRUPTER 4 Sheets-Sheet 4 Filed May 18, 1950 Fig.l3.

INVENTOR Winthrop M. Leeds. 6 BY ATTORNE Patented Aug. 11, 1953 CIRCUIT IN TERRUPTER Winthrop M. Leeds, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 18, 1950, Serial No. 162,656

14 Claims.

The invention relates to circuit interrupters in general, and, more particularly, to are extinguishing structures therefor.

A general object of my invention is to provide an improved circuit interrupter particularly adapted for the lower voltage ranges in which a single pressure-generating break and a single interrupting break are adequate for interruption of the circuit through the pole of the interrupter.

It has been the general practice when applying circuit interrupters of the self-generated fluid flow type, involving a pressure-generating break and an interrupting break, to circuit interrupters of the steel tank type in which terminal bushings extend interiorly within the tank, to provide duplicate units which are generally disposed at the lower ends of the two terminal bushings. One object of my invention is to adapt a self-generating type of fluid flow circuit interrupter to an interrupter of the tank type involving only a single pressure-generating break and a single interrupting break for interrupting the current passing through each pole of the interrupter.

With a pressure-generating break on one terminal of the interrupter and an interrupting break on the other terminal of the interrupter, some means for transmitting the pressure driven fluid, such as oil, from one break to the other is required. Previous solutions to this problem, are set forth in U. S. patent applications filed May 18, 1950, Serial No. 162,655, and filed May 18, 1950, Serial No. 162,657 by me and assigned to the assignee of the instant application, the latter application maturing into U. S. Patent 2,627,566 issued February 3, 1953. The structure set forth in the aforesaid applications utilized a horizontally-disposed cylindrical tube or a horizontal interrupting structure of insulating material for bridging the two terminal bushings of the interrupter. However, horizontal insulating surfaces are known to collect carbon which may in some instances encourage flash-over during arc rupture when high recovery voltage transients are applied to the ends of these horizontal surfaces. When this occurs, it will mean that arcing will take place externally of the extinguishing structure and not internally thereof. The possibility exists that under such conditions arcing might take place between the lower ends of the two terminal bushings, and the resulting pressure during such continued arcing in the liquid would rupture the tank before series breakers closer to the generator would be relayed to function.

It is an object of the present invention to improve the structure by utilizing a conducting pressure transmitting conduit and also employing arc extinguishing units extending an appreciable vertical distance along the direction of the line of separation of the contacts.

Another object is to provide an improved circuit interrupter of the foregoing type in which improved arc extinguishing units are associated with the pressure-generating break and with the interrupting break.

Still a further object is to provide such an interrupter of the foregoing type in which the arc extinguishing units are substantially enclosed at the ends thereof adjacent the terminal bushings.

Further objects and advantages will readily become apparent upon reading the following specification taken in conjunction with the drawings in which:

Fig. 1 is a side elevational view, partially in vertical section,-of a circuit interrupter embodying my invention and shown in the fully open circuit position;

Fig. 2 is an enlarged vertical sectional view through the improved arc extinguishing structure of Fig. 1, the contacts being shown in the closed circuit position;

Fig. 3 is a view similar to that of Fig. 2 but showing the contact structure in the partially open circuit position;

Fig. 4 is a vertical sectional view taken along the line IV-IV of Fig. 2;

Fig. 5 is a vertical sectional view taken along the line VV of Fig. 2;

Fig. 6 is an enlarged bottom plan view of the arc extinguishing structure of Fig. 1;

Fig. 7 is a sectional view taken along the line VII-VII of Fig. 5;

Fig. 8 is a sectional view taken along the line VIII-VIII of Fig. 4;

Fig. 9 is a sectional view taken along the line IXIX of Fig. 4;

Fig. 10 is a vertical sectional view through a modified type of circuit interrupter embodying the principles of my invention and shown in the closed circuit position;

Fig. 11 is a view similar to that of Fig. 10 showing the contact structure in the partially open circuit position;

Fig. 12 is a bottom plan view of the arc extinguishing structures of Figs. 10 and 11;

Fig. 13 is a vertical sectional View through a modified type of circuit interrupter similar in over-all principle to that of Fig. 2 but having the upper ends of the arc extinguishing units substantially enclosed to increase the generation of the pressure within the arc extinguishing units; and

Fig. 14 is a sectional view through a tank type three pole circuit interrupter illustrating the arrangement of the three poles to minimize external flash-over.

Referring to the drawings, and more particularly to Fig. 1 thereof, the reference numeral l designates a suitable enclosure such as a tank filled to the level 2 with a suitable arc extinguishing fluid 3, in this instance circuit breaker oil.

Depending from the cover 4 of the tank I. are two terminal bushings 5, B at the lower ends of which are disposed stationary contact assemblages l, 8.

Movable within the tank I and bridging the contact assemblages l, 8 is a movable arc extinguishing assemblage generally designated by the reference numeral 9. The assemblage 9 includes a pressure-generating arc extinguishing unit l9 and a movable interrupting arc extinguishing unit generally designated by the reference character II.

The two units I0, I I are rigidly secured together and are movable simultaneously by means of conducting conduit means, generally designated by the reference numeral l2. and including two conducting tubes I37, M, as more clearly shown in Fig. 6.

A rod-shaped pressure-generating contact i5 and. a rod-shaped interrupting contact I 6 are rigidly secured. to the extremities of a conducting cross-bar ll,v the latter being reciprocally movable in a vertical direction by an. insulating lift rod l8. Preferably the cross-bar i1 includes a pair of cross-straps |z9 of metallic material. As more clearly shown in- Fig. 2, the lift rod it has an enlarged portion 20, which is arranged to strike a shoulder 2| forming an integral part of the conduit means i2. An. accelerating compression spring 22 is disposed between the shoulder portion 2| and the cross-bar H as shown more clearly in Fig. 2.

The movable arc extinguishing assemblage 9 will now be described. The movable pressuregenerating arc extinguishing unit ill includes an insulating cylinder 24, in which is internally disposed two types of insulating plates. One type is designated by the reference character 28 and is shown more clearly in Fig. 'l. The insulating plate 25 has a cutout portion 2'! of the configuration shown. The other type of insulating plate is designated by the reference character 28' and is similar in exterior configuration to that of the plate 265. However, the plate 28 is provided with a small aperture 29 forming an orifice through which the rod-shaped pressure-generating contact I5 is withdrawn. The orifice insulating plate 28 is also provided with two cutout portions 25, the purpose for which will appear more fully hereinafter. The insulating plates are alternately disposed within the cylinder 25, the lower end of which is threadedly secured at 30 to an upstanding portion. SI of. the casting forming the conduit means E2.

The top-most insulating orifice plate 23 is beveled, as at 32 to accommodate the lower end of the contact assemblage I. As illustrated in Fig. 2, the stationary contact assemblage lincludes a cylindrical housing 33- preferably of conducting material having a tapered lower end 34. Interiorly disposed within. the housing 33 are a plurality of contact segments 35 biased radially inwardly by compression springs 36 to make good contacting engagement with the upper end of the contact rod 15. Flexible conductors 31' may be employed to electrically connect the contact segments 35 with the conducting clamp 33, the latter being threadedly secured to the lower end of the terminal stud 39, and clamped thereto by the nut 40 and bolt 4!.

Positioned at the other end of the conduit means i2 is the interrupting arc extinguishing unit H, which will now be described. An insulating cylinder 43 has its lower end threadedly secured, as at 44, to the casting forming the conduit means i2. Interiorly positioned within the cylinder 43 are a plurality of insulating plates disposed in contiguous relation. The top-most insulating plate is designated by the reference character 45 and merely has an aperture or orifice ll provided therethrough. The upper side of the aperture ll is beveled, as at 32, to ac commodate the tapered lowered end of the housing 48 of. the stationary contact assemblage. 8. The internal construction of the stationary contact assemblage 8 is the same as that of the contact assemblage l, heretofore described, and hence will not need to be further described.

Immediately below the insulating orifice plate 36 is an insulating composite vent plate generally designated by the reference character Ale and including two horizontally spaced segmental insulating plates 58, as shown more clearly in Fig. 8. Each segmental insulating plate 54! has a cutout portion 25, and the spacing between the two insulating plates 5i! provides a pair of diametrically opposed exhaust passages 5|. Apertures 5-2 are provided in the cylinder is to permit unimpeded fiow of fluid, in this instance oil or gaseous products of oil decomposition when heated by an are, out of the interrupting unit H during the interruption process.

Immediately below the vent plate is is a second orifice plate at similar in construction to the top plate it except that no bevel 32 is provided. Immediately below the second orifice plate 46 is an insulating inlet plate 54, the configuration of which is more clearly shown in Fig. 9. The inlet plate 54 has a cutout portion 55 to permit the oil passing through the conduit means it to pass substantially radially inwardly toward the interrupting are established between the rod contact 116 and the stationary contact 8, and designated by the reference character 56 in Fig. 3.

Below the inlet plate 54 is an orifice plate 5i which is similar in construction to the orifice plates 46 previously described except that two cutout portions 53 are provided, the purpose of which will appear more clearly hereinafter. Below the orifice plate 5i is a second vent plate ii) having a construction as previously described. Below the vent plate is a second orifice plate 5i, which is followed by a second inlet plate 54. Below the inlet plate 541 is another orifice plate til.

The operation of my improved circuit interrupter will now be described. In the closed circuit position of the interrupter, as shown in Fig. 2, the electrical circuit therethrough includes terminal stud 39, stationary contact assemblage l, rod-shaped pressure-generating contact iii, conducting crossbar ll, rod-shaped interrupting contact l6, stationary contact assemblage 8 to terminal stud 59.

When it is desired to open the electrical circuit passing through the interrupter, suitable mechanism, not shown, but which is responsive to either manual operation or to the existence of over-load conditions existing in the electrical circuit controlled by the interrupter, functions to cause downward opening movement of the insulating lift rod it. This downward movement of the lift rod it is accelerated by the biasing action exerted by the accelerating compression spring 22, which functions initially to hold the conducting conduit means l2 and the units iii, 5 i upwardly against the stationary contact assemblage l, 8. Consequently, the pressure-generating are 50 (Fig. 3) is established rapidly between the contacts l. i5. and the interrupting are 56 (Fig. 3) is established between the contacts I6, 8 within the respective units I0, I I while the latter remain temporarily positioned against the lower ends of the contact assemblage I, 8.

The establishment of the pressure-generating are 50 within the pressure-generating arc passage 6i, defined by the several insulating plates disposed within the cylinder 24, generates pressure by decomposing the adjacently disposed oil, resulting in a flow of oil outwardly, as shown by the arrows 62 of Fig. '7, within the vent plates 26 and downwardly through the vertical flow channels 63 formed by the alignment of the several cutout portions 25. The oil thus passes downwardly within the unit ID in a manner more clearly shown by the arrows in Fig. 5. The lower ends of the vertical flow channels 63 communicate with the two conducting tubes I3, I4 to permit the passage of oil toward the right, as viewed in Fig. 3, and into the vented right-hand grid I I.

As shown in Fig. 4, the oil passes upwardly from the conducting tubes I3, I4 to strike the interrupting are 56 through the two insulating inlet plates 54. Each insulating inlet plate 54 provides a pair of inlet passages 65 to permit communication between the oil moving upwardly in the vertical flow channels 66 and the interrupting arc passage 64. The oil passes substantially radially inwardly toward the interrupting are 59 through the several pairs of inlet passages 65, and is forced to pass through the apertures or orifices Ail provided by the several orifice plates 51. Contaminated oil flows out of the exhaust passages 5| provided by the composite vent lates 49, as shown by the arrows in Fig. 8.

Interruption of the interrupting are 5% soon follows with a consequent breaking of the electrical circuit passing through the breaker. As the tension relaxes in the accelerating spring 22, the weight of the movable arc extinguishing assemblage 9 causes an initial downward movement of the assemblage 9, made more positive a moment later by engagement of the enlarged portion 29 of the lift rod I8 with the shoulder portion 2! of the assemblage 9. Thus the entire movable assemblage 9 is lowered to the full open circuit position of the interrupter shown in Fig. 1.

It will be observed that during the closing stroke the cross-bar ll will move up initially before any appreciable movement of the heavier assemblage 9 takes place. This will cause the contacts I5, 1 5 to raise relative to the assemblage 9 so that the upper tips of the contacts I5, I 6 approach the top of the units I0, II to engage the stationary contacts I, 8 at substantially the same time as engagement of the units It, I I with the contact assemblage I, 8. Thus, any flashover occurring during the closing stroke with voltage across the terminals of the interrupter will occur in substantially clean oil adjacent the tops of the units I0, I I, and not interiorly thereof.

From the foregoing description of this embodiment of my invention, it will be apparent that I have provided an improved circuit interrupter of the high speed type, particularly adaptable for the lower voltage ranges, that is, 69 kv. and below, in which a single pressure-generating break and a single interrupting break are ade quate for effecting clearing of the circuit. The construction is obviously simple and not susceptible to contamination of the arcing passages during the closing stroke. The conducting conduit means 12 results in the upstanding portion of the units I 0, I I holding the voltage, there being no horizontal surfaces to collect deposits of carbon, and thereby to give rise to hazards of flashover occurring during arc rupture when high recovery voltage transients are applied to the interrupter. It will be observed that in the fully open circuit position of the interrupter, as shown in Fig. 1, two isolated disconnect gaps are provided in clean oil to hold the voltage.

Referring to the construction set forth in Figs. 10-12 it will be observed that in this simpler embodiment of my invention, for applications where the highest speeds of arc interruption are not required, the conducting conduit means I2 is rigidly secured to the lift rod I8. In other words, I employ a clamp 69 securing the lower end of the lift rod I9 to the two conducting tubes I3, I4 as shown by the bottom plan view of Fig. 12. The pressure-generating unit ID has an internal construction identical to that of the unit I0 of Fig. 2, as far as configuration of the insulating plates are concerned. However, in this instance a stationary rod contact H is secured to the clamp I2, the latter being affixed to the lower end of the terminal stud 39. Cooperable with the lower tip of the stationary contact TI is a movable contact 13 biased upwardly by a compression spring I4. Flexible conductors I5 are employed to carry the current from the contact I3 to the casting I6 forming the conducting conduit means I2.

The movable interrupting arc extinguishing unit ll is identical in configuration to that of the movable arc extinguishing unit II of Fig. 2 with the exception that the contact structure is modiiied to incorporate a stationary interrupting contact i3 and a movable interrupting contact I9. Again, the contact 59 is biased upwardly by a compression spring I4, and flexible conductors I5 are employed to permit passage of the current from the movable interrupting contact E9 to the casting 76. Interruption of the circuit follows in a manner previously described, it being noted that here there is a positive interconnection between the lift rod I 8 and the movable arc extinguishing assemblage 89.

In the construction shown in Figs. 10 through 12 it Will be observed that due to the greater inertia of the moving parts, butt contacts II, I3 and 78, I9 are employed to keep the over-all operating time as short as possible. This arrangement, as shown in Figs. 10-12, has the chief advantage of simplicity.

Fig. 13 shows a modified form of interrupter in which the tops of the units 93, 84 are enclosed to bring about the existence of higher pressureconditions within said units in spite of a small downward movement of the units before the arc is extinguished. As set forth, a movable disconnect contact 35 forming an integral portion of a contact cap 86 is cooperable in the closed position with a stationary disconnect contact 87, the latter being clamped to the lower end of the terminal stud 39. A valve 88 is employed including apertures 89 provided in the contact cap 86 and a ring shaped valve plate 99. The latter, in the closed position of the device, rests upon the con tact segments 8| thereby permitting opening of the apertures 89 and the passage of oil therethrough.

During the opening operation the movable disconnect contact separates from the stationary disconnect contact 8! only following are extinction.

Associated with the interrupting unit 84 is a movable disconnect contact 92 cooperable with a connection with Figs. l.9.

stationary disconnect contact :93. The cap structure M'serves to-permit high pressure to .be at- "tained within the interrupting-unit 8d, and the scribed in connection WithFig. 2, higher pressure conditions being attained because of the enclosed structure. Following are extinction, the movable disconnect contacts '85, '92 are withdrawn from the stationary disconnect contacts 81, 93 to insert a pair of isolating gaps in the circuit.

Fig. 14 shows a three pole circuit interrupter with the three poles 9?, 98 andq99 enclosed within a single enclosure or tank 96. Each of the poles ill-99 is ofthe type heretofore described in It will be observed .that the assemblages are alternated so that venting from the interrupting units l l takes place in such manner as tominimize external flash-over. That is, there is no possibility for commingling of the exhaust gases to contaminate the surrounding oil, to the extent of causing flash-over to occur between units during the opening operation. By the construction provided, the possibility of external flash-over is reduced to a mini- -mum, and this results in a very compact arrange ment, as shown, in which the three poles ill, 98 and 99 may be disposed Within a single enclosure or tank 96.

From the foregoing description of several embodiments of my invention, it will be clearly understood that I-have provided an improved form of interrupter particularlyadapted for the lower voltage ranges. It will be noted that for such ranges where a single pressure-generating break and a single interrupting break are adequate for each pole of the interrupter, I have not placed both breaks on a single side of the pole, but have placed one break at one side and the other break at the other side of the pole. Mechanical advantages are thereby obtained. By the use of conducting fluid bridging conduits the construction furthermore minimizes the presence of horizontal surfaces of insulation which might collect carbon deposits, and thereby results in efficient arc extinction with little possibility of flash-over.

Although I have shown and described specific structures, it is to be clearly understood that the same were merely for the purpose or" illustration, and that changes and modifications may readily be made therein by thoseskilled in the art without departing from the spirit and scope of the appended claims.

.I claim as my invention:

1. In a circuit interrupter of the liquid break type, a tank containing an arc extinguishing liquid, two terminal bushings extending into the tank, relatively stationary contact means disposed at the interior end of each terminal bushing, a movable arc extinguishing assemblage including a pressure-generating unit and an interrupting unit hydraulically interconnected by a conducting conduit means, movable contact means including a movable pressure-generating contact and a movable interrupting contact, a movable conducting cross-bar electrically and mechanically connecting the two movable contacts, an operating rod fixed to the cross-bar to cause the actuation of the saline, and a lost- .motion connection between the movable contact means and the movable arc extinguishing assemblage so that during the initial portion of the opening operation only the movable contact means first moves and subsequently, after an appreciable delay, the arc-extinguishing assemblage moves therewith.

2. In a circuit interrupter of the liquid break type, a tank containing an arc extinguishing liquid, two terminal bushings extending into the tank, relatively stationary contact means disposed at the interior end of each terminal bushing, a movable arc extinguishing assemblage including a pressure-generating unit and an interrupting unit hydraulically interconnected by a conducting conduit means, movable contact means including a movable pressure-generating contact and a movable interrupting contact, a conducting cross-bar electrically and mechanically connecting the two movable contacts, an operating rod fixed to the cross-bar to cause the actuation of the same, a lost-motion connection between the movable contact means and the movable arc extinguishing assemblage, means biasing the movable arc extinguishing assemblage to the closed circuit position, and the .operating rod having an actuating portion to forceably drive the extinguishing assemblage therewith during the final portion of the opening operation.

3. In a circuit interrupter of the liquid break type, a tank containing an arc extinguishing liquid, two terminal bushings extending into the tank, relatively stationary contact means disposed at the interior end of each terminal bushing, a movable arc extinguishing assemblage including a pressure-generating unit and an interrupting 'unit hydraulically interconnected by a conducting conduit means, movable contact means including a movable pressuregenerating contact and a movable interrupting contact, a conducting cross-bar electrically and mechanically connecting the two movable contacts, an operating rod fixed to the cross-bar to cause the actuation of the same, a lost-motion connection between the movable contact means and the movable arc extinguishing assemblage so that during the initial portion of the opening operation only the movable contact means first moves and subsequently, after an appreciably delay, the arc-extinguishing assemblage moves therewith, and the movable contacts being movable through the units to engage the stationary contact means in the closed circuit position of the interrupter.

4. In a circuit interrupter of the liquid break type, a tank containing an arc extinguishing liquid, two terminal bushings extending into the tank, relatively stationary contact means disposed at the interior end of each terminal bushing, a movable arc extinguishing assemblage including a pressure-generating unit and an interrupting unit hydraulically interconnected by a conducting conduit means, both the pressure-generating and interrupting units being formed in part of insulating material extending upwardly vertically from the ends of the conducting conduit means, movable contact means movable with the assemblage and including a movable pressure-generating contact and a movable interrupting contact, and an operating rod fixed to the conducting conduit means to cause blage' including a pressure-generating unit and an interrupting unit hydraulically interconnectedby a conducting conduit means, movable contact means having a lost motion connection with the assemblage including a movable pressure-generating contact and a movable interrupting contact, an insulating operating rod for actuating the assemblage and the movable contact means, and the assemblage remaining momentarily stationary during the initial portion of the opening operation while the movable contacts move relative thereto establishing arcing within the pressure-generating and interrupting units.

6. In a circuit interrupter of the liquid break type, a tank containing an arc extinguishing liquid, two terminal bushings extending into the tank, relatively stationary contact means disposed at the interior end of each terminal bushing, a movable arc extinguishing assemblage including a pressure-generating unit and an interrupting unit hydraulically interconnected by a conducting conduit means, movable contact means including a movable pressuregenerating contact and a movable interrupting contact, a conducting cross-bar electrically and mechanically connecting the two movable contacts, an operating rod fixed to the cross-bar to cause the actuation of the same, and a lostmotion connection between the movable contact means and the movable arc extinguishing assemblage, movable disconnect means associated with the end of each unit and contacting the stationary contact means in the closed circuit position, and the movable contacts pulling away from the movable disconnect means interiorly of the units during the opening operation.

'7. In a circuit interrupter of the liquid break type, a tank containing an arc extinguishing liquid, two terminal bushings extending into the tank, relativel stationary contact means disposed at the interior end of each terminal bushing, a movable arc extinguishing assemblage including a pressure-generating unit and an interrupting unit hydraulically interconnected by a conducting conduit means, movable contact means including a movable pressure-generating contact and a movable interrupting contact, a conducting cross-bar electrically and mechanically connecting the two movable contacts, an operating rod fixed to the cross-bar to cause the actuation of the same, a lost-motion connection between the movable contact means and the movable arc extinguishing assemblage, movable disconnect means associated with the end of each unit and contacting the stationary contact means in the closed circuit position, the movable contacts pulling away from the movable disconnect means interiorly of the units during the opening operation, and the movable disconnect means enclosing said ends of the units to increase the pressure formed therein during the opening operationv 8. In a circuit interrupter of the liquid break type, a tank containing an arc extinguishing liquid, two terminal bushings extending into the tank, relatively stationary contact means disposed at the interior end of each terminal bushing, a movable arc extinguishing assemblage including a pressure-generating unit and an interrupting unit hydraulically interconnected by a conducting conduit means, movable contact means including a movable pressure-generating contact and a movable interrupting contact, a conducting cross-bar electrically and mechanical- 10- ly connecting the two movable contacts-an operating rod fixed to the cross-bar to cause the actuation of the same, a lost-motion connectionbetween the movable contact means and the movable arc extinguishing assemblage, movable disconnectmeans associated with the end of each unit and contacting the stationary contact means in the closed circuit position, the movable contacts pulling away fromthe movable disconnect means interiorly of the units during the opening operation, the movable disconnectmea-ns enclosing said ends of the units to increase the" pressure formed therein during the opening operation, and valve means associated with the movable disconnect means to vent the units at the end of the opening operation.

9. In a circuit interrupter of the liquid break type, a tank containing an arc extinguishing liquid, two terminal bushings extending into the tank, relatively stationary contact means disposed at the interior end of each terminal bushing, a movable arc extinguishing assemblage including a pressure-generating unit and an interrupting unit hydraulically interconnected by a conducting conduit means, movable contact means including a movable pressure-generating contact and a movable interrupting contact, a conducting cross-bar electrically and mechanically connecting the two movable contacts, an operating rod fixed to the cross-bar to cause the actuation of the same, a lost-motion connection between the movable contact means and the mov able arc extinguishing assemblage, and the conducting conduit means comprising two metallic tubes between which the cross-bar operates.

10. A liquid break circuit interrupter including a pair of spaced rod-shaped stationary contacts, a movable pressure-generating insulating arc extinguishing unit, a movable interrupting insulating arc extinguishing unit, hollow conducting conduit means electrically and hydraulically interconnecting the two units, both the pressure-generating and interrupting units extending upwardly from the ends of the conducting conduit means, an operating rod fixed to the conduit means intermediate the ends thereof to cause the actuation of the same, each unit having a passage formed therein open at one end into which the rod-shaped stationary contacts enter during the final portion of the closing stroke, a pair of movable contacts disposed at the other end of the passages and engaging the stationary contacts in the closed circuit position, and the stationary contacts being completely removed from the units in the fully open circuit position of the interrupter.

11. In a circuit interrupter of the liquid break type, a tank containing an arc-extinguishing liquid, two terminal bushings extending into the tank, relatively stationary contact means disposed at the interior end of each terminal bushing, a movable arc-extinguishing assemblage including a pressure-generating unit and an interrupting unit hydraulically interconnected by a conducting conduit means, both the pressuregenerating and interrupting units being in part composed of insulating material and extending an appreciable distance vertically upwardly at the two ends of the conducting conduit means, movable contact means including a movable pressure-generating contact and a movable interrupting contact, a movable conducting crossbar electrically and mechanically connecting the two movable contacts, an operating rod fixed to the crossbar to cause the actuation of the same, and

a lost-motion connection between themovable contact means and the movable arc-extinguishing assemblage.

12. In a circuit interrupter of'the liquid break type, a tank containing an arc-extinguishing liquid, two terminal bushings extending into the tank, relatively stationary contact means disposed at the interior end of each terminal bushing, a movable arc-extinguishing assemblage including a pressure-generating unit and an interrupting unit hydraulically interconnected by a conducting conduit means, both the pressuregenerating and interrupting units extending vertically upwardly an appreciable distance at the two ends of the conducting conduit means and being composed at least in part of insulating material, and movable contact means electrically interconnecting the pressure-generating and interrupting units. I

13. In a circuit interrupter of theliquid break type, a tank containing an arc-extinguishing liquid, two terminal bushings extending into the tank, relatively stationary contact means disposed at the interior end of each terminal bushing, a movable arc-extinguishing assemblage including a pressure-generating unit and an interrupting unit hydraulically interconnected by a conducting conduit means, both the pressuregenerating and interrupting units being at least in part composed of insulating material and extending vertically upwardly an appreciable distance at the outer ends of the conducting conduit means, movable contact means including a movable pressure-generating contact and a movable interrupting contact, a conducting cross-bar elec- 1 trically and mechanically connecting the two movable contacts, an operating rod fixed to the cross-bar to cause the actuation of the same, a lost-motion connection between the movable contact means and the movable arc-extinguishing assemblage, means biasing the movable arc-extinguishing assemblage to the closed circuit poi2 sition, and'the operating rod having anactuating portion to forceably drive the extinguishing assemblage therewith during the final portion of the opening operation.

14. In a circuit interrupter of the liquidbreak type, a tank containing anarc-extinguishing-liquid, two terminal bushings extending into the:

tank, relatively stationary contact means: disposed at the interior end of each terminal bushing, a movable arc-extinguishing assemblage in.- cluding a pressure-generating unit andan inter+ rupting unit hydraulically interconnected by av conducting conduit means, both the pressuregenerating and interrupting units being at least in part composed of insulating material and extending vertically upwardly an appreciable distance at the outer two ends of the conducting: conduit means, movable contact means including a movable pressure-generating contact andv a movable interrupting contact, a conducting cross-bar. electrically andmechanically connecting the two movable" contacts, an operatingrod fixed tothe cross-bar: to cause the actuation of the same, a lost-motion connectionbetween the movable contact means and the movable" arc:- extinguishing assemblage, and'the movable con:-

tacts movable through theunits' to engage thev Number. Name 7 Date 2,019,348 Hobson Oct; 29, 1935 2,156,450 Cole May 2, 1939 2,196,008 Cole Apr. 2,. 1940 2,228,232 Hilliard Jan. 7, 1941 FOREIGN PATENTS Number Country Date 413,751 Great Britain July 26, 1934 

